Scientists create superconducting thin films

Oct 08, 2008

Ivan Bozovic

(PhysOrg.com) -- One major goal on the path toward making useful superconducting devices has been engineering materials that act as superconductors at the nanoscale -- the realm of billionths of a meter. Such nanoscale superconductors would be useful in devices such as superconductive transistors and eventually in ultrafast, power-saving electronics.

In the October 9, 2008, issue of Nature, scientists at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory report that they have successfully produced two-layer thin films where neither layer is superconducting on its own, but which exhibit a nanometer-thick region of superconductivity at their interface. Furthermore, they demonstrate the ability to elevate the temperature of superconductivity at this interface to temperatures exceeding 50 kelvin (-370°F), a relatively high temperature deemed more practical for real-world devices.

"This work provides definitive proof of our ability to produce robust superconductivity at the interface of two layers confined within an extremely thin, 1-2-nanometer-thick layer near the physical boundary between the two materials," said physicist Ivan Bozovic, who leads the Brookhaven thin film research team. "It opens vistas for further progress, including using these techniques to significantly enhance superconducting properties in other known or new superconductors."

Bozovic foresees future research investigating different combinations of non-superconducting materials. "Further study of the temperature-enhancement mechanism might even tell us something about the big puzzle — the mechanism underlying high-temperature superconductivity, which remains one of the most important open problems in condensed matter physics," he said.

Bozovic's team had reported in 2002 the bizarre observation that the critical temperature — the temperature below which the sample superconducts — could be enhanced by as much as 25 percent in bilayers of two dissimilar copper-based materials. However, at that time, the scientists had no understanding of what caused this enhancement and in which part of the sample the superconductivity was located.

To investigate this further, they synthesized more than 200 single-phase, bilayer and trilayer films with insulating, metallic, and superconducting blocks in all possible combinations and of varying layer thickness. The films were grown in a unique atomic-layer-by-layer molecular beam epitaxy system designed and built by Bozovic and coworkers to enable the synthesis of atomically smooth films as well as multilayers with perfect interfaces. "The greatest technical challenge was to prove convincingly that the superconducting effect does not come from simple mixing of the two materials and formation of a third, chemically and physically distinct layer between the two constituent layers," Bozovic said. Collaborators at Cornell University ruled out this possibility using atomic-resolution transmission electron microscopy to identify the samples' constituent chemical elements, proving that the layers indeed remained distinct.

"It is too early to tell what applications this research might yield," Bozovic said, "but already at this stage we can speculate that this brings us one big step closer to fabrication of useful three-terminal superconducting devices, such as a superconductive field-effect transistor." In such a device, one would be able to switch the transistor from the superconducting to the resistive state by means of an external electric field, controlled by applying a voltage and using the third (gate) electrode. Circuits built from such devices would be much faster and use less power than the current ones based on semiconductors.

"No matter what the applications, this work is a nice demonstration of our ability to engineer and control materials at sub-nanometer scale, with designed and enhanced functionality," Bozovic said.

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User comments : 17

Another step closer to something practical. Though I have seen so many such steps, and it seems there is still a lot of road to travel. I remember when I first read about carbon 60. Back then, I was certain we would have achieved practical small scale superconductivity by now.

My mistake, even more embarrassing is I consulted that exact page before posting. Appears it has been reached in the late 80s...? Even so I find it personally discouraging advancements are coming so slow. :/ I guess they've been chasing Cooper pairs so long...

The fact is that high temperature superconduction does occur between the crystallographic layers of the copper oxide ceramics. I have already solved this mechanism more than 5 years ago, but cannot get it published because it also proves that Cooper Pairs are NOT the cause of superconduction; also not in the low temperature metals. I have just now had a paper rejected by Nature (without even sending it for peer review) which explains all the properties of disordered thin superconducting thin films which the exablishment could not explain over the last 70 years. Again, I am sure that this was done because the mechanism proves that Cooper Pairs are not involved in superconduction. We thought that the mentality displayed by Galileo's peers is not present anymore. It is still alive and well when Lawrence Krauss can write BS in New Scientist claiming that editors must be "our gatekeepers": i.e. he basically argues that "editors must act as censors". It is thus not surprising that it has become impossible to publish new ideas if these ideas do not conform with accepted dogma. And then Krauss arrogates himself the right to criticise the "intellegent designers". I am not defending the ID's here but it sticks in my throat when a so-called scientist like Krauss can throw around cliches like: "Peer review is imperfect. But the good stuff will always rise to the top". Has he got experimental proof for this? I doubt it. If not, he is violating the most sacred rule of scientific debate: He will do science a favour by just shutting up!

ShadowRam: BE EXCITED: We do have it: But nobody is interested because it means that Cooper Pairs are figments of Cooper's imagination. In fact, there is no such a thing as a metallic superconductor. For a material to superconduct it must become a dielectric or else it cannot cancel an applied, static, conservative electric-field as had been experimentally discovered by Onnes. To cancel such a field, one requires static dielectric polarisation: THIS CANNOT HAPPEN IN A METAL WHILE A CURRENT IS FLOWING WHETHER SCATTERING OCCURS OR NOT. It is thus ironic that the BCS model cannot explain how such a field is being cancelled. One would have thought that this defining aspect of superconduction should have been the first property that required an explanation!

Hi earls,
I will send you a copy when I know who you are and if you undertake confidentiality until I get it published: If ever!!
If you are interested, send me an e-mail through the following company
info@cathodixx.com

@ johanfprins (and others with paradigm changing results), if you want to be taken seriously (which it seems that you do), start by publishing small and build your way up. Nature and Science WILL NEVER PUBLISH something that is massively controversial unless there is CLEAR, PEER REVIEWED, DOCUMENTED EVIDENCE of said material. Attend noteworthy conferences and submit abstracts for presentation/poster sessions. I would suggest APS or other relavent physics groups or the Applied Supercondcutivity Conference held every 2 years. Although, if you are using non-standard model physics, I would really suggest staying away from ASC.

For example: start with a paper/talk on unusual observations, then go to a paper/talk on more research confirming unusual observations that can be confirmed by others. If you make it look like "magic", it will be dismissed as hocus-pocus-mumbo-jumbo. This way, you can get experts in the field, or other fields for that matter, to look at these systems and try to determine if you have missed something (ex. perpetual motion machines, even well known scientists get tripped up sometimes).

Also, if metals can not be superconductors, can you explain to me why (element symbol,[Tc]): Al [1.20], Hg [4.15], Mo [0.92], Nb [9.26], Pb [7.19], Ta [4.48], Ti [0.39], V [5.30], Zn [0.88] are all superconductors and have well established superconducting phase transitions? For that matter, why are alloys of Nb-Ti and Nb-Sn routinely used for superconducting coils?

Thanks for the advice. I have tried most of it but got blocked all the way. I believe it is because the implications are too "horrible to contemplate". It could mean that quantum-field theory is not totally correct; for example, the Higg's boson etc. However, I think I am starting to break through after many agonising years. I am now just pointing out one undeniable fact and that is the following: That the BCS model cannot explain how an applied, static, conservative electric-field is cancelled as soon as superconduction sets in. The latter is THE defining characteristic which allowed Onnes to discover superconduction in 1911 and it should have been the first characteristic that required explaining. The fact is that an applied, static, conservative electric-field can only be cancelled by static dielectric polarisation. The latter is not possible within any metal, also not one which is perfect (i.e. no scattering). This demands that a metal must first undergo a phase-transition to a dielectric phase before it can superconduct. It sounds paradoxical, but it is not possible otherwise. Thus all the metals you have named are "metals" above the critical temperature, but become "dielectrics" below the critical temperature Tc: i.e. the charge-carriers must be localised states which can polarise. The reason why superconsuction can occur, is that such a localised state can move by means of quantum-fluctuations as allowed by Heisenberg's uncertainty relationship for energy and time.
I am attaching the abstract of my latest attempt to get published:

"It is an incontrovertible, elementary, experimentally-proven, self-consistent fact of physics that an applied, static, conservative electric-field can only be cancelled within a material by means of an equal and opposite static, conservative electric-field generated by static dielectric-polarisation. Within a superconducting phase, an applied, static, conservative electric-field must thus be cancelled in exactly this manner at the positions of the superconducting charge-carriers: If not, the charge-carriers will be accelerated: Newton%u2019s laws will then mandate the presence of a voltage-difference over two contacts. The original measurements by Onnes would then not have been possible. The bi-electrons forming Cooper-pairs %u201Cbond%u201D by transient-polarisation (virtual phonons): Static dielectric-polarisation is thus impossible at the positions of these entities. Here it is postulated that each superconducting charge-carrier must be a localised %u201Cstationary%u201D, harmonic electronic-orbital anchored by an induced, localised, %u201Cstationary%u201D lattice-charge (Wigner 1938). Such an electronic-orbital can polarise statically relative to its anchor-charge to cancel the force on it by an applied, static, conservative electric-field. Coherent charge-transport, without violating this static-polarisation, occurs when the inter-orbital distances are less than a critical coherence-length. Quantum-fluctuations, allowed by Heisenberg%u2019s uncertainty relationship, then enable these electronic-orbitals to %u201Cbreak free%u201D from their anchor-charges and move to the positions of adjacent orbitals. The orbitals at the latter anchor-charges are replaced: They %u201Cbreak free%u201D and move further, etc. Since this movement is generated by consecutive, coherent quantum-fluctuations, any orbital, after having replaced an adjacent orbital, does not have any kinetic energy which would mandate resistive-dissipation. It is only under these conditions that an electric-current can flow without generating electrical-resistance. Cooper-pairs maintain kinetic energy."

I must say that I find it highly unlikely that you, or anyone for that matter has disproved BCS theory. The theory is 51 years old and has a great deal of experimental evidence backing it up. You cannot apply a static electric field to a superconductor because it maintains a zero voltage state as long as the current in it is less than Ic( not necessarily the thermodynamic Ic). Experimentally it is not feasible to voltage bias a superconductor when it is superconducting. Think about it. It "wants" to maintain 0 Voltage yet you are applying a voltage across a resistor in parallel. What wins out there? It has nothing to do with the superconductor expelling the E-field, or canceling it as you suggest, and everything to do with Ohm's law (with the SC approximated as a very low resistance Ohmic resistor). I suggest you study simple circuits and understand what is going on before you waste any more of your, and any one else's time. By the way experimentalists use current bias in their measurements.

It seems like this type of pseudoscience is almost pathological. I see it in so many places and it all follows the same pattern. Some person comes up with a theory that proves a long held theory/model/result is completely wrong and claims that it is an injustice/conspiracy when his or her "work" is not published. This person then resorts to posting his or her findings on as many internet message boards whenever a topic close to his or hers is discussed.

Hi Rob,
My problem is that your explanation is not even pseudoscience. I do understand my physics and cicuits very well and I do know that an applied voltage over two contacts can only fall to zero when the applied static conservative electric field is cancelled by static dielectric polarisation between the contacts. There is no other mechanism. Go read your high school books on physics: If you are able to understand them.

It is scientific claptrap to write that " it wants to have zero voltage but the voltage is over another resistor". The experimental fact is that at temperatures above the critical temperature there is a voltage over the superconductor and the bias resistor. As soon as superconduction sets in the voltage over the superconductor is cancelled. This can only occur if the conservative electric-field is cancelled between the contacts of the superconductor. And the latter can only occur by an opposite field generated by static dielectric polarisation. If this were not so we would not have had capacitors.

The argument that BCS is 51 years old and therefore sacrosant exposes you as being a non-scientific, dogmatic, and probably an illiterate fundamentalist. Galileo's detractors had Ptolemy's model which was 2000 years old and which (even today) "has a great deal of experimental evidence backing it up". Even so it is wrong!! I suggest that you should try and understand physics. If you had studied physics you should sue your professors for having been incompetent.

It is unbelievable: I have just had comments from a senior physicist who is employed through one of NASA's subsidiaries and whose knowledge of physics is just as bad, if not worse, than that of Rob. No wonder NASA has to hitch rides on Russian space vehicles. It is clearly not a lack of money but a massive dumbing down of American scientists since the 1960's. I will thus bend down as low as I can and formulate the problem with BCS on a level which USA-scientists hopefully (but I do despair) will be able to understand.

The SIMPLE fact is the following: When there is a voltage V over two contacts a distance d apart then (according to Newton's laws) there MUST be an electric field E between the contacts so that Ed=V (1).
This is true whether:
1. No current is flowing
2. A current is flowing
3. The charge carriers is being scattered
4. The charge carriers is not being scattered

Above the critical temperature there IS a voltage V over a SUPERCONDUCTING material which superconducts below the critical temperature (even when there is a bias resistor with its own voltage Vb as there usually will be). When cooling the superconductor through its critical temperature the voltage over it falls to ZERO (i.e. it shifts to appear over the bias resistor which now has a voltage V Vb over it). THIS DEMANDS ACCORDING TO Eq. 1 THAT THE ELECTRIC-FIELD E MUST BE CANCELLED WITHIN THE SUPERCONDUCTOR (Here in South Africa even our primary school pupils know this: So what is wrong with NASA's scientits?: The s has been deliberately dropped!). Thus, since Onnes' discovery nearly 100 years ago the primary aspect that must be explained is HOW THIS ELECTRIC-FIELD IS CANCELLED AS SOON AS SUPERCONDUCTION KICKS IN. This has NEVER been explained YET and CANNOT be modelled by BCS EVEN THOUGH THIS THEORY IS ALREADY 51 YEARS OLD.

Are there scientists in the USA who can understand the logic above. If not, George Bush should cancel the scientific budget completely!!

Hello Johanfprins,I think that there an ambiguity in the word "Cancelled" when you say that "THE ELECTRIC-FIELD E MUST BE CANCELLED WITHIN THE SUPERCONDUCTOR". I first assume that the current is less than the critical current. Strictly speaking, I would rather say "THE ELECTRIC-FIELD E is zero WITHIN THE SUPERCONDUCTOR". This means that it is not necessary to invoke any dielectric polarisation to counter balance anything.

Now, if the current is higher than the critical current, then the electric field is not steady: the time dependant electric field results from electrodynamic stuctures - called vortices - moving across the sample, in a direction perpendicular to the applied current. They carry one (or several) flux quanta (value = h/2e) surrounded by circular currents (hence, the name vortex) so that the magnetic flux looks like a (cylindrical) bundle. Lenz's law can be written either E = v x B or V=h/2e x dn/dt, where v is the speed of the vortices and n is the number of vortices crossing the line between your contacts. And the voltage V can be measured with anything resembling the so-called "4 probes" method (the contacts are placed so that it measures the voltage without any error), but one easily gets only the DC component of this series of pulses, one for each vortex...

So in no case it is necessary to invoke dielectric properties... sorry !(I am a french physicist, not working for NASA !-)Best regards

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